Amateur Extra Licensing Class Presented by W5YI Arlington, Texas Antennas.

Amateur Extra Licensing Class

Presented byW5YI

Arlington, Texas

Antennas

Amateur Radio Extra ClassElement 4 Course Presentation

ELEMENT 4 Groupings

• Rules & Regs• Skywaves & Contesting• Outer Space Comms• Visuals & Video Modes• Digital Excitement with Computers & Radios• Modulate Your Transmitters• Amps & Power Supplies• Receivers with Great Filters

Amateur Radio Extra ClassElement 4 Course Presentation

ELEMENT 4 Groupings

• Oscillate & Synthesize This!• Circuits & Resonance for All!• Components in Your New Rig• Logically Speaking of Counters• Optops & OpAmps Plus Solar• Test Gear, Testing, Testing 1,2,3• Antennas• Feedlines & Safety

Amateur Radio Extra Class

Antennas• E9A16… The radiation resistance of an antenna is the value of a

resistance that would dissipate the same amount of power as that radiated from an antenna.

• E9A05… Antenna height and conductor length/diameter ratio, and location of nearby conductive objects determine the radiation resistance of an antenna.

• E9A06… The term for the ratio of the radiation resistance of an antenna to the total resistance of the system is antenna efficiency.

Efficiency = (RR/RT) x 100%

RR = Radiation Resistance

RT = Total Resistance


Antennas• E9A07… Radiation resistance plus ohmic resistance are included in

the total resistance of an antenna system.

• E9A11… Antenna efficiency is calculated by the equation:

(radiation resistance / total resistance) x 100%.

Can also be calculated by the equation:

Efficiency = Radiated Power / Input power

• E9B01… The orientation of its electric field (E Field) determines the free-space polarization of an antenna.


Antennas

Propagating Electromagnetic Waves

Electric Field Magnetic Field

Vertical Polarization


Antennas• E9A12… The efficiency of an HF quarter-wave grounded vertical

antenna can be improved by installing a good radial system.

• E9A13… Soil conductivity is the most important factor in determining ground losses for a ground-mounted vertical antenna operating in the 3-30 MHz range.

• E9C15… The conductivity and dielectric constant of the soil in the area of the antenna strongly affects the shape of the far-field, low-angle elevation pattern of a vertically polarized antenna.


Antennas• E9C12… When a vertically polarized antenna is mounted over

seawater versus rocky ground the far-field elevation pattern low-angle radiation increases.

• E9C17… The main effect of placing a vertical antenna over an imperfect ground is that it reduces low-angle radiation.

• E9D14… A thin, flat copper strap several inches wide would be best for minimizing losses in a station's RF ground system.

The thin copper strap will have lower inductive reactance making it a lower loss to the earth ground point.

A lower angle of radiation means longer skip.


Antennas•

E9D15… A connection to 3 or 4 interconnected ground rods driven into the earth would provide the best RF ground for your station.

Copper bonded ground rods

Tower groundedwith three 8’ ground rods


Antennas• E9C01… The radiation pattern

of two 1/4-wavelength vertical antennas spaced 1/2-wavelength apart and fed 180 degrees out of phase is a figure-8 oriented along the axis of the array.

• E9C02… The radiation pattern of two 1/4-wavelength vertical antennas spaced 1/4-wavelength apart and fed 90 degrees out of phase is a cardioid.

Two vertical ¼ wave antennasFeed points180º out of phase½ wavelength apart

Two ¼ wavelength verticals¼ wavelength apart withFeed points 90º out of phase


Antennas• E9C03… The radiation

pattern of two 1/4-wavelength vertical antennas spaced 1/2-wavelength apart and fed in phase is a figure-8 broadside to the axis of the array.

• E9A08… A dipole constructed from one wavelength of wire forming a very thin loop is a folded dipole antenna.

Two 1/4 wavelength verticals1/2 wavelength apart,feed points in phase

Folded Dipole Antenna Made from 300 Ohm Twin-Lead


Antennas• E9D10… The approximate feed-point impedance at the center of a

folded dipole antenna is 300 ohms.

• E9A04… One needs to know the feed point impedance of an antenna to match impedances for maximum power transfer from a feed line.

• E9A01… An isotropic Antenna is a theoretical antenna used as a reference for antenna gain. An isotropic source radiates equally in all directions

Isotropic Radiator Pattern


Antennas• E9A03… An Isotropic antenna has no (zero) gain in any direction.

• E9A02… A 1/2-wavelength dipole has 2.15 dB gain compared to an isotropic antenna.

• E9A14… If an antenna has 3.85 dB gain over a 1/2-wavelength dipole then it has 6 dB gain over an isotropic antenna.

The gain over isotropic source for an antenna with a 3.85 dB gain over a dipole antenna would be an additional 2.14 dB of gain.

Remember dipole gain over an isotropic source is 2.14 dB

3.85 dB +1.14dB

= 5.99dB

(Actually 2.14 dB gain, the test question answer is rounded to 2.15 dB)


Antennas• E9A15… An antenna has 9.85 dB of

gain

• E9D11… A loading coil is often used with an HF mobile antenna to cancel capacitive reactance.

• E9D08… The bandwidth of an antenna is decreased as it is shortened through the use of loading coils.

Remember that a dipole has 2.14 dB of gain as referenced to an isotropic antenna.

12 dB - 2.14 dB

gain =9.86dB

over a 1/2-wavelength dipolewhen it has 12 dB of gain over an isotropic antenna.


Antennas• E9A10… Antenna bandwidth is the frequency range over which an

antenna satisfies a performance requirement.

• E9D06… An HF mobile antenna loading coil should have a high ratio of reactance to resistance to minimize losses.

• E9D05… For a shortened vertical antenna, a loading coil is placed near the center of the vertical radiator to minimize losses and produce the most effective performance.

• E9D09… An advantage of using top loading in a shortened HF vertical antenna is improved radiation efficiency.

Performance examples would be – Gain - SWR or impedance - Beam width - etc


Antennas• E9D13… The resistance decreases and the capacitive reactance

increases at the base feed-point of a fixed-length HF mobile antenna as the frequency of operation is lowered.

• E9D12… An advantage of using a trapped antenna is that it may be used for multi-band operation.

• E9D07… A disadvantage of using a multi-band trapped antenna is that it might radiate harmonics.

Schematic of trap antenna


Antennas• E9B09… You can approximate beamwidth of a directional antenna

by noting the two points where the signal strength of the antenna is 3 dB less than maximum and compute the angular difference.

• E9B10… The “Method of Moments” computer program technique is commonly used for modeling antennas.


Antennas• E9B14… The abbreviation NEC stands for Numerical

Electromagnetics Code when applied to antenna modeling programs.

• E9B13… The disadvantage of NEC-based antenna modeling programs is that computing time increases as the number of wire segments is increased.

• E9B12… The disadvantage of decreasing the number of wire segments in an antenna model below the guideline of 10 segments per half-wavelength is that the computed feed-point impedance may be incorrect.

• E9B15… SWR vs. frequency charts, polar plots of the far-field elevation and azimuth patterns, and antenna gain can be obtained by submitting (entering) the details of a proposed new antenna to a modeling program.


Antennas

• E0A01… The difference between the radiation produced by radioactive materials and the electromagnetic energy radiated by an antenna is that RF radiation does not have sufficient energy to break apart atoms and molecules. Radiation, from radioactive sources does.

• E0A09… Beryllium Oxide, an insulating material commonly used as a thermal conductor for some types of electronic devices, is extremely toxic if broken or crushed and the particles are accidentally inhaled.

• E9B11… The principle that the “Method of Moments” analysis is based on is a wire that is modeled as a series of segments, each having a distinct value of current.

• E9A09… Antenna gain is the numerical ratio relating the radiated signal strength of an antenna in the direction of maximum radiation to that of a reference antenna.

Gain is generally expressed in dB relative to either an Isotropic source or a dipole.


Antennas• E0A07… The "far-field" zone of an antenna is the area where the

shape of the antenna pattern is independent of distance.• E9B02… In the antenna radiation pattern shown in Figure E9-1, the 3-

dB beamwidth is 50 degrees.

Note the intersection of the 3dB circle is at approximately + & – 25 degrees for a total beamwidth of 50 degrees.

Figure E9-1


Antennas• E9B03… In the antenna radiation pattern shown in Figure E9-1,

the front-to-back ratio is 18 dB. Figure E9-1

Rear lobe is half way between the -12dB and the -24dB points.


Antennas• E9B04… In the antenna radiation pattern shown in Figure E9-1, the

front-to-side ratio is 14 dB.

Figure E9-1

Side lobes14 dB


Antennas• E9B05… When a directional antenna is operated at different

frequencies within the band for which it was designed the gain may exhibit significant variations.

• E9B06… If a Yagi antenna is designed solely for maximum forward gain the front-to-back ratio decreases.

• E9B07… If the boom of a Yagi antenna is lengthened and the elements are properly retuned, usually the gain increases.

Element spacing affects bandwidth responseBoom length influences gain


Antennas

• E9B08… The total amount of radiation emitted by a directional (gain) antenna compared with the total amount of radiation emitted from an isotropic antenna will be the same when each is driven by the same amount of power. There will be no difference in total radiated power between the two antennas.

Remember the key word is total power.

In an isotropic antenna power is equally radiated in all directions. In a gain antenna the power is focused in one direction so in that direction it is stronger but in other directions it is weaker.

Total power is the sum of all power in all directions assuming both antennas are 100% efficient.


Antennas• E3C07… The radiation pattern of a 3-element, horizontally

polarized beam antenna will vary with height above ground. The main lobe takeoff angle will decrease with increasing height.

• E3C10… The performance of a horizontally polarized antenna mounted on the side of a hill when compared with the same antenna mounted on flat ground will have a main lobe takeoff angle that decreases in the downhill direction.

Antenna

Antenna

Radiation Pattern

Distorted Radiation Pattern


Antennas• E9C08… An antenna elevation pattern over real ground is shown in

Figure E9-2.

• E9C09… The elevation angle of peak response in the antenna radiation pattern shown in Figure E9-2 is 7.5 degrees.

Figure E9-2

Figure E9-2

7.5 degrees


Antennas• E9C10… The front-to-back ratio of the radiation pattern shown in

Figure E9-2 is 28 dB.

• E9C11… Four elevation lobes appear in the forward direction of the antenna radiation pattern shown in Figure E9-2.

Figure E9-2

Back lobes Front lobes

Four elevation lobes

Figure E9-2


Antennas

• E9C14… The electric field will be horizontally oriented for a Yagi with three elements mounted parallel to the ground.

• E9D02… One way to produce circular polarization, when using linearly polarized antennas, is to arrange two Yagi antennas perpendicular to each other with the driven elements at the same point on the boom and fed 90 degrees out of phase.

Element 4 Extra Class Question Pool

Valid July 1, 2008

Through

June 30, 2012

Antennas

E9A16 What is meant by the radiation resistance of an antenna?

A. The combined losses of the antenna elements and feed line

B. The specific impedance of the antennaC. The value of a resistance that would

dissipate the same amount of power as that radiated from an antenna

D. The resistance in the atmosphere that an antenna must overcome to be able to radiate a signal

E9A05 Which of the following factors determine the radiation resistance of an antenna?

A. Transmission-line length and antenna height

B. Antenna height and conductor length/diameter ratio, and location of nearby conductive objects

C. It is a physical constant and is the same for all antennas

D. Sunspot activity and time of day

E9A06 What is the term for the ratio of the radiation resistance of an antenna to the total resistance of the system?

A. Effective radiated powerB. Radiation conversion lossC. Antenna efficiencyD. Beamwidth

E9A07 What is included in the total resistance of an antenna system?

A. Radiation resistance plus space impedance

B. Radiation resistance plus transmission resistance

C. Transmission-line resistance plus radiation resistance

D. Radiation resistance plus ohmic resistance

E9A11 How is antenna efficiency calculated?

A. (radiation resistance / transmission resistance) x 100%

B. (radiation resistance / total resistance) x 100%C. (total resistance / radiation resistance) x 100%D. (effective radiated power / transmitter output) x

100%

E9B01 What determines the free-space polarization of an antenna?

A. The orientation of its magnetic field (H Field)

B. The orientation of its free-space characteristic impedance

C. The orientation of its electric field (E Field)D. Its elevation pattern

E9A12 How can the efficiency of an HF quarter-wave grounded vertical antenna be improved?

A. By installing a good radial systemB. By isolating the coax shield from

groundC. By shortening the verticalD. By reducing the diameter of the

radiating element

E9A13 Which is the most important factor that determines ground losses for a ground-mounted vertical antenna operating in the 3-30 MHz range?

A. The standing-wave ratioB. Base currentC. Soil conductivityD. Base impedance

E9C15 What strongly affects the shape of the far-field, low-angle elevation pattern of a vertically polarized antenna?

A. The conductivity and dielectric constant of the soil in the area of the antenna

B. The radiation resistance of the antenna and matching network

C. The SWR on the transmission lineD. The transmitter output power

E9C12 How is the far-field elevation pattern of a vertically polarized antenna affected by being mounted over seawater versus rocky ground?

A. The low-angle radiation decreasesB. The high-angle radiation increasesC. Both the high- and low-angle radiation

decreaseD. The low-angle radiation increases

E9C17 What is the main effect of placing a vertical antenna over an imperfect ground?

A. It causes increased SWRB. It changes the impedance

angle of the matching networkC. It reduces low-angle radiationD. It reduces losses in the

radiating portion of the antenna

E9D14 Which of the following types of conductor would be

best for minimizing losses in a station's RF ground

system?

A. A resistive wire, such as a spark-plug wireB. A thin, flat copper strap several inches

wideC. A cable with 6 or 7 18-gauge conductors in

parallelD. A single 12 or 10 gauge stainless steel

wire

E9D15 Which of these choices would provide the best RF ground for your station?

A. A 50-ohm resistor connected to ground

B. A connection to a metal water pipeC. A connection to 3 or 4 interconnected

ground rods driven into the EarthD. A connection to 3 or 4 interconnected

ground rods via a series RF choke

E9C01 What is the radiation pattern of two 1/4-wavelength vertical antennas spaced 1/2-wavelength apart and fed 180 degrees out of phase?

A. A cardioidB. OmnidirectionalC. A figure-8 broadside to the

axis of the arrayD. A figure-8 oriented along the

axis of the array

E9C02 What is the radiation pattern of two 1/4-wavelength vertical antennas spaced 1/4-wavelength apart and fed 90 degrees out of phase?

A. A cardioidB. A figure-8 end-fire along the axis

of the arrayC. A figure-8 broadside to the axis

of the arrayD. Omnidirectional

E9C03 What is the radiation pattern of two 1/4-wavelength vertical antennas spaced 1/2-wavelength apart and fed in phase?

A. OmnidirectionalB. A cardioidC. A Figure-8 broadside to the axis of the

arrayD. A Figure-8 end-fire along the axis of

the array

E9A08 What is a folded dipole antenna?

A. A dipole one-quarter wavelength longB. A type of ground-plane antennaC. A dipole constructed from one

wavelength of wire forming a very thin loop

D. A hypothetical antenna used in theoretical discussions to replace the radiation resistance

E9D10 What is the approximate feed-point impedance at the center of a folded dipole antenna?

A. 300 ohmsB. 72 ohmsC. 50 ohmsD. 450 ohms

E9A04 Why would one need to know the feed point impedance of an antenna?

A. To match impedances for maximum power transfer from a feed line

B. To measure the near-field radiation density from a transmitting antenna

C. To calculate the front-to-side ratio of the antenna

D. To calculate the front-to-back ratio of the antenna

E9A01 Which of the following describes an isotropic Antenna?

A. A grounded antenna used to measure earth conductivity

B. A horizontal antenna used to compare Yagi antennas

C. A theoretical antenna used as a reference for antenna gain

D. A spacecraft antenna used to direct signals toward the earth

E9A03 Which of the following antennas has no gain in any direction?

A. Quarter-wave verticalB. YagiC. Half-wave dipoleD. Isotropic antenna

E9A02 How much gain does a 1/2-wavelength dipole have compared to an isotropic antenna?

A. 1.55 dBB. 2.15 dBC. 3.05 dBD. 4.30 dB

E9A14 How much gain does an antenna have over a 1/2-wavelength dipole when it has 6 dB gain over an isotropic antenna?

A. 3.85 dBB. 6.0 dBC. 8.15 dBD. 2.79 dB

E9A15 How much gain does an antenna have over a 1/2-wavelength dipole when it has 12 dB gain over an isotropic antenna?

A. 6.17 dBB. 9.85 dBC. 12.5 dBD. 14.15 dB

E9D11 Why is a loading coil often used with an HF mobile antenna?

A. To improve receptionB. To lower the lossesC. To lower the QD. To cancel capacitive

reactance

E9D08 What happens to the bandwidth of an antenna as it is shortened through the use of loading coils?

A. It is increasedB. It is decreasedC. No change occursD. It becomes flat

E9A10 What is meant by antenna bandwidth?

A. Antenna length divided by the number of elements

B. The frequency range over which an antenna satisfies a performance requirement

C. The angle between the half-power radiation points

D. The angle formed between two imaginary lines drawn through the element ends

E9D06 Why should an HF mobile antenna loading coil have a high ratio of reactance to resistance?

A. To swamp out harmonicsB. To maximize lossesC. To minimize lossesD. To minimize the Q

E9D05 For a shortened vertical antenna, where should a loading coil be placed to minimize losses and produce the most effective performance?

A. Near the center of the vertical radiator

B. As low as possible on the vertical radiator

C. As close to the transmitter as possible

D. At a voltage node

E9D09 What is an advantage of using top loading in a shortened HF vertical antenna?

A. Lower QB. Greater structural strengthC. Higher lossesD. Improved radiation

efficiency

E9D13 What happens at the base feed-point of a fixed-length HF mobile antenna as the frequency of operation is lowered?

A. The resistance decreases and the capacitive reactance decreases

B. The resistance decreases and the capacitive reactance increases

C. The resistance increases and the capacitive reactance decreases

D. The resistance increases and the capacitive reactance increases

E9D12 What is an advantage of using a trapped antenna?

A. It has high directivity in the higher-frequency bands

B. It has high gainC. It minimizes harmonic

radiationD. It may be used for multi-band

operation

E9D07 What is a disadvantage of using a multi-band trapped antenna?

A. It might radiate harmonicsB. It can only be used for single-

band operationC. It is too sharply directional at

lower frequenciesD. It must be neutralized

E9B09 How can the approximate beamwidth of a directional antenna be determined?

A. Note the two points where the signal strength of the antenna is 3 dB less than maximum and compute the angular difference

B. Measure the ratio of the signal strengths of the radiated power lobes from the front and rear of the antenna

C. Draw two imaginary lines through the ends of the elements and measure the angle between the lines

D. Measure the ratio of the signal strengths of the radiated power lobes from the front and side of the antenna

E9B10 What type of computer program technique is commonly used for modeling antennas?

A. Graphical analysisB. Method of MomentsC. Mutual impedance analysisD. Calculus differentiation with

respect to physical properties

E9B14 What does the abbreviation NEC stand for when applied to antenna modeling programs?

A. Next Element ComparisonB. Numerical Electromagnetics

CodeC. National Electrical CodeD. Numeric Electrical

Computation

E9B13 Which of the following is a disadvantage of NEC-based antenna modeling programs?

A. They can only be used for simple wire antennas

B. They are not capable of generating both vertical and horizontal polarization patterns

C. Computing time increases as the number of wire segments is increased

D. All of these answers are correct

E9B12 What is a disadvantage of decreasing the number of wire segments in an antenna model below the guideline of 10 segments per half-wavelength?

A. Ground conductivity will not be accurately modeled

B. The resulting design will favor radiation of harmonic energy

C. The computed feed-point impedance may be incorrect

D. The antenna will become mechanically unstable

E9B15 What type of information can be obtained by submitting the details of a proposed new antenna to a modeling program?

A. SWR vs. frequency chartsB. Polar plots of the far-field

elevation and azimuth patternsC. Antenna gain D. All of these answers are correct

E0A01 What, if any, are the differences between the radiation produced by radioactive materials and the electromagnetic energy radiated by an antenna?

A. There is no significant difference between the two types of radiation

B. Only radiation produced by radioactivity can injure human beings

C. RF radiation does not have sufficient energy to break apart atoms and molecules; radiation from radioactive sources does

D. Radiation from an antenna will damage unexposed photographic film, ordinary radioactive materials do not cause this problem

E0A09 Which insulating material commonly used as a thermal conductor for some types of electronic devices is extremely toxic if broken or crushed and the particles are accidentally inhaled?

A. MicaB. Zinc oxideC. Beryllium OxideD. Uranium Hexaflouride

E9B11 What is the principle of a Method of Moments analysis?

A. A wire is modeled as a series of segments, each having a distinct value of current

B. A wire is modeled as a single sine-wave current generator

C. A wire is modeled as a series of points, each having a distinct location in space

D. A wire is modeled as a series of segments, each having a distinct value of voltage across it

E9A09 What is meant by antenna gain?

A. The numerical ratio relating the radiated signal strength of an antenna in the direction of maximum radiation to that of a reference antenna

B. The numerical ratio of the signal in the forward direction to that in the opposite direction

C. The ratio of the amount of power radiated by an antenna compared to the transmitter output power

D. The final amplifier gain minus the transmission-line losses (including any phasing lines present)

E0A07 What is the "far-field" zone of an antenna?

A. The area of the ionosphere where radiated power is not refracted

B. The area where radiated power dissipates over a specified time period

C. The area where radiated field strengths are obstructed by objects of reflection

D. The area where the shape of the antenna pattern is independent of distance

E9B02 In the antenna radiation pattern shown in Figure E9-1, what is the 3-dB beamwidth?

A. 75 degreesB. 50 degreesC. 25 degreesD. 30 degrees

Figure E9-1

120 60

30

0

-30

-60-120

-150

150

180

Free-SpacePattern

-3-6

-12

-24

E9B03 In the antenna radiation pattern shown in Figure E9-1, what is the front-to-back ratio?

A. 36 dBB. 18 dBC. 24 dBD. 14 dB

Figure E9-1

120 60

30

0

-30

-60-120

-150

150

180

Free-SpacePattern

-3-6

-12

-24

E9B04 In the antenna radiation pattern shown in Figure E9-1, what is the front-to-side ratio?

A. 12 dBB. 14 dBC. 18 dBD. 24 dB

Figure E9-1

120 60

30

0

-30

-60-120

-150

150

180

Free-SpacePattern

-3-6

-12

-24

E9B05 What may occur when a directional antenna is operated at different frequencies within the band for which it was designed?

A. Feed-point impedance may become negative

B. The E-field and H-field patterns may reverse

C. Element spacing limits could be exceeded

D. The gain may exhibit significant variations

E9B06 What usually occurs if a Yagi antenna is designed solely for maximum forward gain?

A. The front-to-back ratio increases

B. The front-to-back ratio decreases

C. The frequency response is widened over the whole frequency band

D. The SWR is reduced

E9B07 If the boom of a Yagi antenna is lengthened and the elements are properly retuned, what usually occurs?

A. The gain increasesB. The SWR decreasesC. The front-to-back ratio

increasesD. The gain bandwidth

decreases rapidly

E9B08 How does the total amount of radiation emitted by a

directional (gain) antenna compare with the total amount of radiation emitted from an isotropic antenna, assuming each is driven by the same amount of power?

A. The total amount of radiation from the directional antenna is increased by the gain of the antenna

B. The total amount of radiation from the directional antenna is stronger by its front to back ratio

C. There is no difference between the two antennas

D. The radiation from the isotropic antenna is 2.15 dB stronger than that from the directional antenna

E3C07 How does the radiation pattern of a 3-element, horizontally polarized beam antenna vary with height above ground?

A. The main lobe takeoff angle increases with increasing height

B. The main lobe takeoff angle decreases with increasing height

C. The horizontal beam width increases with height

D. The horizontal beam width decreases with height

E3C10 How does the performance of a horizontally polarized antenna mounted on the side of a hill compare with the same antenna mounted on flat ground?

A. The main lobe takeoff angle increases in the downhill direction

B. The main lobe takeoff angle decreases in the downhill direction

C. The horizontal beam width decreases in the downhill direction

D. The horizontal beam width increases in the uphill direction

E9C08 What type of antenna pattern over real ground is shown in Figure E9-2?

A. ElevationB. AzimuthC. Radiation

resistanceD. Polarization

Figure E9-2

Over Real Ground

180

150

120 90

60

30

0 -40 -30 -20 -10

E9C09 What is the elevation angle of peak response in the antenna radiation pattern shown in Figure E9-2?

A. 45 degreesB. 75 degreesC. 7.5 degreesD. 25 degrees

Figure E9-2

Over Real Ground

180

150

120 90

60

30

0 -40 -30 -20 -10

E9C10 What is the front-to-back ratio of the radiation pattern shown in Figure E9-2?

A. 15 dBB. 28 dBC. 3 dBD. 24 dB

Figure E9-2

Over Real Ground

180

150

120 90

60

30

0 -40 -30 -20 -10

E9C11 How many elevation lobes appear in the forward direction of the antenna radiation pattern shown in Figure E9-2?

A. 4B. 3C. 1D. 7

Figure E9-2

Over Real Ground

180

150

120 90

60

30

0 -40 -30 -20 -10

E9C14 How would the electric field be oriented for a Yagi with three elements mounted parallel to the ground?

A. VerticallyB. HorizontallyC. Right-hand ellipticallyD. Left-hand elliptically

E9D02 What is one way to produce circular polarization when using linearly polarized antennas?

A. Stack two Yagis, fed 90 degrees out of phase, to form an array with the respective elements in parallel planes

B. Stack two Yagis, fed in phase, to form an array with the respective elements in parallel planes

C. Arrange two Yagis perpendicular to each other with the driven elements at the same point on the boom and fed 90 degrees out of phase

D. Arrange two Yagis collinear to each other, with the driven elements fed 180 degrees out of phase

Amateur Extra Licensing Class Presented by W5YI Arlington, Texas Antennas.

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Transcript of Amateur Extra Licensing Class Presented by W5YI Arlington, Texas Antennas.